Gov't offers heat stress index website in English in bid to prevent heatstroke

TOKYO -- The Ministry of the Environment is providing English-language information about the heat stress index on its website in a bid to prevent illnesses caused by intense heat, which has become a major threat to health and even life in Japan in recent summers.

The website, designed for viewing by both smartphones and personal computers, indicates the intensity of the heat effect throughout the country in five colors, from blue (almost safe) to red (danger). It also provides two-day predictions for the heat stress index, as well as data for each observation point nationwide.

The heat stress index, also called the Wet Bulb Globe Temperature (WBGT), is one of the empirical indices showing the heat stress an individual is exposed to. It is calculated incorporating factors such as humidity, sunlight and reflection intensities and atmospheric temperature.

According to the ministry website, the number of people suffering from heatstroke shoots up rapidly when the WBGT, which is denoted in degrees but is different from normal air temperature, exceeds the upper threshold of the "Warning" level (25-28 degrees), when the air temperature is between 28 and 31 degrees Celsius.

For the warning level indicated in yellow, people are advised to rest often. When the index is at the "Severe Warning" level of orange, people are advised to refrain from heavy exercise. At the "Danger" level shown in red, people should stop all exercise.

According to the Fire and Disaster Management Agency, almost 10,000 people were rushed to hospitals across Japan due to heat-related illnesses during the week through July 15. As many as 12 people died due to heatstroke. The Japan Meteorological Agency said that temperatures in prefectures in central Japan topped 40 degrees Celsius -- higher than the average human body temperature of 36.5 Celsius -- in the cities of Tajimi and Mino in Gifu Prefecture on July 18. It was the first time in five years that the mercury rose to that level in the nation. (By Hiroaki Wada, Staff Writer)